In manufacturing a frame member and bumper reinforced member of an automobile, or a member for a construction structure and an exterior, there is a case of performing a bending process of curving a long member such as an aluminum section material and a steel material in a longitudinal direction thereof.
With respect to a bending method of a long member, for example, as described in Japanese Patent Laid-Open Publication No. 2002-066642 (see paragraph 0027 and FIG. 1), there is the bending method of using a bending die curved like an arc in accordance with a bent form of a workpiece (object to be worked) of the long member, and a linear die linearly extended.
As a bending apparatus for performing the bending method, there is one comprising: a table having a work face where a bending die and a linear die are placed; and a pair of rollers provided on the work face, wherein each of the rollers is configured to be driven and rotated at a predetermined position on the work face.
According to the bending method described in the Japanese Patent Laid-Open Publication No. 2002-066642, firstly, frond-end sides of the bending die and the linear die are fitted with each other, and the dies are placed on the work face in a state of their back-end sides being opened. Moreover, a workpiece is attached to a forming face of the linear die, and a front end of the workpiece is held by a front end of a forming face of the bending die.
When the front ends of the bending die and the linear die where the workpiece is set are sent between each of the rollers, the dies pass between each of the rollers from a back to front thereof in a state of being pinched in a die closing direction by each of the rollers.
With respect to the bending die like an arc, because a region having passed between each of the rollers is moved in a direction away from the linear die, the bending die and the linear die result in a state of their front end sides being opened. At this time, because the front end of the workpiece is held on the work face of the bending die, the workpiece is separated from the linear die in a state of being stuck to the forming face of the bending die, and is bent along the forming face of the bending die.
According to the bending method described in the Japanese Patent Laid-Open Publication No. 2002-066642, because a bending stress can be uniformly acted on a workpiece, it is possible to improve a working accuracy. Furthermore, it is possible to speedily adapt various forms of bending.
However, according to the bending method described in the Japanese Patent Laid-Open Publication No. 2002-066642, because the bending die and the linear die move from the back to front of each of the rollers, and it is necessary to ensure a space at the back and front of each of the rollers in order that the dies move, there is a problem that the bending apparatus results in being wholly jumbo sized.
Furthermore, an inertia force acts on the bending die and the linear die after they pass each of the rollers, it is difficult to stop the dies. Furthermore, after the bending, it is necessary to return the bending die and the linear die, which are moved to the front of each of the rollers, to the back of each of the rollers.
Thus, according to the bending method described in the Japanese Patent Laid-Open Publication No. 2002-066642, because a worker needs to handle the bending die and the linear die for every one bending, there is a problem that an operation is troublesome and a work efficiency is reduced.
Particularly, in bending a workpiece whose axial section is large, because axial sections of the bending die and the linear die are large in proportion to a size of the workpiece, and weight of the dies increases, it is difficult for a worker to handle the dies.